The entire disclosure of Japanese Patent Application No. 2008-190204, filed Jul. 23, 2008, is expressly incorporated herein by reference.
1. Technical Field
The present invention relates to a liquid supply device including a supply pump provided in a liquid supply passage, a first unidirectional valve provided in the upstream side of the supply pump, and a second unidirectional valve provided on the downstream side of the supply pump, and a liquid ejecting apparatus.
2. Related Art
In the past, an ink jet printer as a liquid ejecting apparatus printed a text, an image, or the like by ejecting ink droplets as a liquid onto a target (a sheet, etc.) from a printing head. An ink cartridge (a liquid storing member) as an ink supply source supplying ink to the printing head is mounted on such a kind of printer. As an ink supplying method of supplying ink from the ink cartridge to the printing head, there is known a method of using a water head difference based on a difference between an ink surface of the ink cartridge and the height of nozzles of the printing head or a method of supplying ink by use of a pump.
In the ink supply device (a liquid supply device) using the pump, there is known a pressurizing supply method (for example, JP-A-2002-192751 (FIG. 2, etc.)) of supplying ink by sending air pressurized by a pressurizing pump to an ink cartridge and pressurizing an ink pack accommodated in the ink cartridge or a method (JP-A-2006-272661 (FIGS. 2, 4, 6, 8, 10, etc.)) of supplying ink by driving a pump provided in an ink passage and ejecting the ink sucked from an ink cartridge located on the upstream side of the ink passage toward the downstream side of the ink passage.
An ink supply device disclosed in JP-A-2062-272661 includes a pulsation type pump such as a diaphragm type pump and a pair of unidirectional valves (check valves) provided in the upstream side (an input side) and the downstream side (an output side) of the pump, respectively. The unidirectional valve (a first unidirectional valve) on the upstream side is opened by the depressurization of the ink upon the sucking drive of the pump, and maintains a valve-closed state when the pressure of the ink is increased upon the ejecting drive of the pump. On the other hand, the unidirectional valve (a second unidirectional valve) on the downstream side maintains a valve-closed state upon the sucking drive of the pump and is opened when the pressure of the ink is increased upon the ejecting drive of the pump.
In the ink supply device disclosed in JP-A-2062-272661, the pumps and the first and second unidirectional valves are formed by interposing a flexible member (a diaphragm forming member) between upper and lower cases. In this configuration, a part of the flexible member functions as a diaphragm of the pump and another part of the flexible member functions as a valve body of the unidirectional valve.
Since the portion around the pump and the valves in the flexible member function as a sealing portion, the upper and lower cases have to be joined in a compressed state to the flexible member. In the past, a method of joining the upper and lower cases was performed by fastening fastening members such as screws or bolts.
However, when the tightening force is too strong due to the non-uniformity of the tightening force of screws, the flexible member is excessively pressed and deformed. In this case, even when the sealing portion of the portion around the pump and the valves in the flexible member is excessively pressed and deformed, a sealing function is not damaged.
However, in some cases, a part of rubber or the like excessively pressed and deformed is pushed toward the pump chamber or the inside of the valve chamber and thus the diaphragm or the valve body becomes loose. For example, when the valve body becomes loose, the time taken to open or close the unidirectional valve may be different from the designed time, thereby causing non-uniformity in the opening or closing time. The non-uniformity in the opening or closing time results in a delay of the valve closing time or the valve closeness of the first unidirectional valve (a sucking valve) on the upstream side and the second unidirectional valve (an ejecting valve) on the downstream side not completely closing, for example. In this case, when a delay of the valve closing time of the ejecting valve occurs upon starting the sucking drive or the valve does not completely close, the ink on the downstream area is depressurized and thus a necessary ink pressurizing value may not be guaranteed or the delay of the valve closing time of the sucking valve may occur upon starting the ejecting drive. Alternatively, when the delay of the valve closing time of the sucking valve occurs upon starting the ejecting drive or the valve does not completely close, the ink which has to be ejected may flow backward to the ink cartridge. In particular, when the valve closeness of the sucking valve is incomplete, a problem occurs in that the ink pressurized in the liquid supply device flows backward and thus leaks from the ink supply needle when the ink cartridge is detached to exchange the ink cartridge. Moreover, when the upper and lower cases are joined by the use of the fastening members such as screws, the work required for fastening the fastening members such as plural screws becomes very troublesome.